A Philippine senator has vowed to continue an official inquiry into President Rodrigo Duterte's incendiary anti-drug trafficking campaign despite his accusations and threats against her.

Senator Leila de Lima called Duterte's attacks an "abuse and misuse of executive power" during an emotional speech Thursday in Manila. De Lima has launched a legislative probe into the killings of at least 1,000 suspected drug traffickers since Duterte took office in June, having won election on a pledge of ridding the archipelago of illicit drugs and drug criminals.

The senator said Duterte's accusations, which he made during a speech Wednesday marking the 115th anniversary of the country's police force, had temporarily caused her to reconsider her position. "It is clear that what is being done to me is what will happen to anyone who does not bow to the wishes of the president," she said.

President Duterte also lashed out against the United Nations in his speech Wednesday, saying the world body was making "a very stupid proposition" in criticizing his efforts. U.N. Secretary-General Ban Ki-moon has condemned Duterte's apparent support of extrajudicial killings, calling them "a breach of fundamental human rights and freedoms."

The president questioned why the U.N. would be "so easily swayed into interfering into the affairs of this republic" since only 1,000 people have been killed.

Official tallies say at least half of those killed were involved in shootouts with police.